Storage method and apparatus for distributed file system

ABSTRACT

Provided are a storage method and apparatus for a distributed file system. The method includes: determining access times to a same file in preset time; and migrating the file to a storage device with higher performance than that of a current storage device according to the access times. Through the technical solution, tiered storage is performed on files in the distributed file system according to access enthusiasm of the files, that is, a file with a high access frequency in the preset time is migrated to a storage device with higher performance, and a file fragment storage location is associated with file fragment access enthusiasm through differential storage, so that IOPS pressure between storage devices is balanced and the overall performance is improved.

TECHNICAL FIELD

The disclosure relates to the field of communications, and in particularto a storage method and apparatus for a distributed file system (DFS forshort).

BACKGROUND ART

Distributed storage achieves mass storage and rapid deployment of databy saving data in a plurality of disks of a plurality of servers in adistributed manner. With the update of types of storage devices, newstorage devices will continuously join the disk cluster; as a result,distributed storage must support plug-and-play for these storagedevices.

Different storage devices have different capacities and performancesfrom each other. How to utilize the space and performance of thesestorage devices to a maximum degree is a problem needing emphasizedconcern. Original disk reading and writing strategies mainly concern thespace balancing between a disk and a file access server, or use a randompolling and selection strategy. Other load balancing technologies in therelevant art mainly concern the selection of a file access server whenwriting a file according to load information about file access serversat the time when writing the file.

However, the load balancing strategies in the relevant art do not solvethe problem of the load brought to the disk by high-frequency access toa hot file when reading out a file, and the system has the followingdefect: input/output operation per second (IOPS for short) which can besupported by different storage devices are different. At first,fragments for storing a file are selected according to a disk spacebalancing strategy or random strategy. Under a same load, a highperformance storage device can operate stably, but a reading delayphenomenon may occur on a low performance storage device.

In the condition where high and low performance storage devices coexist,the low performance storage device will become a short slab of theperformance of all distributed storage devices, and this will bepresented more apparently when performing a file reading operation. Justbecause of the short slab effect of the low performance storage device,the performance difference between different storage devices will lowerthe overall performance of a disk cluster, resulting in that theperformance of the high performance storage device cannot be usedmaximumly.

SUMMARY

The embodiments of the disclosure provide a storage method and apparatusfor a distributed file system, so as to at least solve the problem ofthe load brought to the disk by high-frequency access to a hot file whenreading out a file in the relevant art.

According to one embodiment of the disclosure, a storage method for adistributed file system is provided, including: determining access timesto a same file in preset time; and migrating the file to a storagedevice with higher performance than that of a current storage deviceaccording to the access times.

In the described embodiment, migrating the file to the storage devicewith higher performance than that of the current storage deviceaccording to the access times includes: determining that the accesstimes exceed a preset threshold value; determining, from all storagedevices, a storage device with higher performance than that of thecurrent storage device and having an idle block; and migrating the fileto the determined storage device.

In the described embodiment, after determining that the access timesexceed the preset threshold value, the method further includes: settingan access enthusiasm attribute of the file as hot.

In the described embodiment, before determining the access times to asame file in preset time, the method further includes: respectivelydetermining an input/output operation per second (IOPS) limit and acurrent IOPS of each storage device in the distributed file system;respectively calculating a ratio of the current IOPS to the TOPS limitof each storage device; and respectively comparing the ratio with apreset critical value; and if the ratio is greater than the presetcritical value, determining that it is needed to migrate the file withhigher access times than a preset threshold value in a current storagedevice.

In the described embodiment, after determining that it is needed tomigrate the file with higher access times than the preset thresholdvalue in the current storage device, the method further includes:receiving a reading request for the file, and adding one to the accesstimes to the file.

In the described embodiment, before determining the access times to asame file in preset time, the method further includes: a file accessserver calculating an TOPS of a storage device corresponding to the fileaccess server; and the file access server reporting the IOPS to ametadata server according to a predetermined period.

In the described embodiment, after migrating the file to the storagedevice with higher performance than that of the current storage deviceaccording to the access times, the method further includes: checkingwhether a ratio of a current IOPS to an IOPS limit of each storagedevice is not greater than a critical value according to a predeterminedperiod; if the ratio value is not greater than the critical value,stopping migrating the file in the current storage device; and if theratio is greater than the critical value, continuing migrating the filewith higher access times than a preset threshold value in the currentstorage device.

According to another embodiment of the disclosure, a storage apparatusfor a distributed file system is provided, wherein the storage apparatusis applied to a metadata server and includes: a first determinationcomponent, configured to determine access times to a same file in presettime; and a migration component, configured to migrate the file to astorage device with higher performance than that of a current storagedevice according to the access times.

In the described embodiment, the migration component includes: a firstdetermination unit, configured to determine that the access times exceeda preset threshold value; a second determination unit, configured todetermine, from all storage devices, a storage device with higherperformance than that of the current storage device and having an idleblock; and a migration unit, configured to migrate the file to thedetermined storage device.

In the described embodiment, the apparatus further includes: a seconddetermination component, configured to respectively determine aninput/output operation per second (IOPS) limit and a current IOPS ofeach storage device; a calculation component, configured to respectivelycalculate a ratio of the current IOPS to the IOPS limit of each storagedevice; a comparison component, configured to respectively compare theratio with a preset critical value; and a third determination component,configured to, if the ratio is greater than the preset critical value,determine that it is needed to migrate the file with higher access timesthan a preset threshold value in a current storage device.

Through the embodiments of the disclosure, tiered storage is performedon files in the distributed file system according to access enthusiasmof the files, that is, a file with a high access frequency in the presettime is migrated to a storage device with higher performance, and a filefragment storage location is associated with file fragment accessenthusiasm through differential storage, so that IOPS pressure betweenstorage devices is balanced and the overall performance is improved.

BRIEF DESCRIPTION OF THE DRAWINGS

Drawings, provided for further understanding of the disclosure andforming a part of the specification, are used to explain the disclosuretogether with embodiments of the disclosure rather than to limit thedisclosure. In the accompanying drawings:

FIG. 1 is a flowchart of a storage method for a distributed file systemaccording to an embodiment of the disclosure;

FIG. 2 is a system architecture diagram of a storage method for adistributed file system according to an embodiment of the disclosure;

FIG. 3 is a flowchart of a storage method for a distributed file systemaccording to an example embodiment of the disclosure;

FIG. 4 is a structural block diagram of a storage apparatus for adistributed file system according to an embodiment of the disclosure;

FIG. 5 is a structural block diagram I of a storage apparatus for adistributed file system according to an example embodiment of thedisclosure; and

FIG. 6 is a structural block diagram II of a storage apparatus for adistributed file system according to an example embodiment of thedisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be noted that the embodiments and the characteristics of theembodiments can be combined with each other if no conflict is caused.The disclosure will be explained below with reference to the drawingsand in conjunction with the embodiments in detail.

The embodiments of the disclosure provide a storage method for adistributed file system. FIG. 1 is a flowchart of a storage method for adistributed file system according to an embodiment of the disclosure. Asshown in FIG. 1, the following step S102 to step S104 are included.

Step S102, access times to a same file in preset time are determined.

Step S104, the file is migrated to a storage device with higherperformance than that of a current storage device according to theaccess times.

In the relevant art, the problem of the load brought to the disk byhigh-frequency access to a hot file when reading out a file is notsolved. In the embodiments of the disclosure, tiered storage isperformed on files in the distributed file system according to accessenthusiasm of the files, that is, a file with a high access frequency inthe preset time is migrated to a storage device with higher performance,and a file fragment storage location is associated with file fragmentaccess enthusiasm through differential storage, so that IOPS pressurebetween storage devices is balanced and the overall performance isimproved.

It should be noted that a file with a low access frequency may also bemigrated to a storage device with low performance in preset time, so asto avoid the occupation of too much storage space of the storage devicewith high performance.

Step S104 includes: determining that the access times exceed a presetthreshold value; determining from all the storage devices a storagedevice with higher performance than that of a current storage device andhaving an idle block; and migrating the file to the determined storagedevice with higher performance. In the present example embodiment, inthe case where the access times exceed a preset threshold value,determining a storage device which may store the file, and performingmigration when the determined storage device has an idle block canensure the accuracy of file migration, avoiding the case where thestorage device does not have any idle block but the file is migrated tothe storage device, which may result in file loss.

In an example embodiment, after determining that the access times exceeda preset threshold value, an access enthusiasm attribute of the file maybe set as hot. The access enthusiasm of a file is displayed in themanner of an attribute so as to facilitate user checking.

In another example embodiment, before determining access times to a samefile in preset time, whether the current storage device needs filemigration is confirmed, i.e. whether the load of the current storagedevice has exceeded a critical value (or referred to as a warning value)is determined, which can be achieved by the following operations:respectively determining an IOPS limit and a current IOPS of eachstorage device in the distributed file system; respectively calculatinga ratio of the current TOPS to the IOPS limit of each storage device;respectively comparing the ratio with a preset critical value; and ifthe ratio is greater than the preset critical value, determining that itis needed to migrate the file with higher access times than a presetthreshold value in a current storage device. In the present exampleembodiment, whether to perform migration is determined according to notonly the load condition of the current storage device but also theaccess enthusiasm of the file in the device. The time and frequency of auser to access a file are both random. Unreasonable file migration maylower the usage efficiency of the storage device, and quicken the lossdegree of the storage device.

The above-mentioned process of determining whether it is needed tomigrate the file according to the load of the storage device is also acondition for initiating a tiered storage flow (which may be referred toas a critical value algorithm). There are mainly two factors whichaffect initiating migration: (1) whether the IOPS of the storage devicereaches a designated warning value, after the IOPS approaches thecritical value, the processing speed of the storage device will bedecreased significantly, and tired storage must be initiated; and (2)whether the system has sufficient idle high performance storage fragmentavailable, if not, the tiered storage flow is ignored.

In practical applications, whether tiered storage needs to be initiatedis determined according to the file access enthusiasm, the IOPS limitand the current IOPS statistical value of each storage device (forexample, a disk) and the idle block condition of the storage device. Forexample, assuming that the identification of whether to initiate tieredstorage is y; the IOPS limit of a disk i is IOPS_(i); the current IOPSstatistical value of the disk i is CIOPS_(i); and the identification ofwhether there are sufficient idle blocks is f, only when a file is a hotfile and the ratio value of CIOPS_(i)/IOPS_(i) is greater than acritical value a, and a target storage device has sufficient idleblocks, will the tiered storage flow be initiated.

In an example embodiment, after determining that it is needed to migratethe file with higher access times than a preset threshold value in acurrent storage device, the above-mentioned method further includes:receiving a reading request for the file, and adding one to the accesstimes to the file. In the present example embodiment, in the case ofdetermining that it is needed to perform file migration according to theload condition of the current storage device, receiving a readingrequest for a file of the current storage device and calculating accesstimes to the file may avoid performing statistics on the accessenthusiasm of a file in each storage device to some extent whichincreases the burden for a metadata server. In practical applications, atiered storage switch is provided in the metadata server, and the switchis turned on after determining that it is needed to perform migration,and then the statistics on access times is performed.

In an example embodiment, in the above-mentioned process of determiningwhether it is needed to perform migration according to the load of astorage device, an IOPS of the storage device is used. The TOPS may beobtained according to the following method: a file access servercalculating an IOPS of a storage device corresponding to the file accessserver; and the file access server reporting the IOPS to a metadataserver according to a predetermined period.

In practical applications, a storage device IOPS checking timer isprovided in a service program of the file access server. Once the timeris turned on, the timer invokes an operating system interface tocalculate an IOPS parameter of each storage device (for example, a disk)in the present file access server, and the file access server uses thetimer to report the IOPS of each disk at regular time intervals to ametadata server.

After step S104, it can be determined whether the load of the originalstorage device of the file has recovered to a value less than thecritical value after the file is migrated. If not, the access enthusiasmof a file therein is continued to be monitored, and the file is migratedwhen a condition is met. This may be achieved according to the followingsteps: checking whether a ratio of a current IOPS to an IOPS limit ofeach storage device is not greater than a critical value according to apredetermined period; if the ratio value is not greater than thecritical value, stopping migrating the file in a current storage device;and if the ratio is greater than the critical value, continuingmigrating a file with higher access times than a preset threshold valuein the current storage device.

The above-mentioned storage method for a distributed file systemoptimizes the implementation solution of distributed file system storagein the related art, and can be understood as tiered file fragmentstorage. The tiered storage refers to storing a file with a high accessfrequency in a storage device with high performance, that is, thestorage devices are divided into two tiers: storage devices with lowperformance and storage devices with high performance. By means of theabove-mentioned solution, IOPS pressure between storage devices isbalanced, and the overall performance is improved, thereby achieving themaximum usage of the compatibility and performance of storage deviceswith different performances.

In order to make the technical solutions and implementation methods ofthe embodiments of the disclosure more apparent, the implementationprocess is described in details in combination with example embodimentsbelow.

The system architecture for achieving the above-mentioned solutionincludes a metadata server 22, a file access client 24, a file accessserver 26 and a storage device cluster 28, as shown in FIG. 2, thesecomponents will be described respectively hereinafter.

The metadata server 22 is responsible for managing metadata informationabout all files in the current distributed file system, such as filenames, data blocks, and providing operations such as metadata writing inand query for the file access client 24. The embodiments of thedisclosure adds an access pressure weight value (i.e. access times inpreset time) on the basis of a metadata file list, and when the weightvalue of the file exceeds a configured threshold value, all thefragments of the file stored in low performance storage areas aremigrated to high performance storage areas, without affecting the accessof the current user.

The file access client 24 is responsible for providing an interfaceinvoking service similar to a standard file system for the currentdistributed file system oriented application program; initiating anaccess request, acquiring data and then returning same to theapplication program; and migrating, when the metadata server 22initiates a migration request, file fragments to other file accessservers according to a fragment list in the request.

The file access server 26 is responsible for interacting with thestorage device cluster 28 in the current distributed file system, andperforming practical reading and writing operations on data blocks; inresponse to a data reading or writing request of the file access client24, reading data from the storage device cluster 28 and returning sameto the file access client 24, or reading data from the file accessclient 24 and writing same in the storage device cluster 28. The fileaccess server 26 as shown in FIG. 2 includes a file access server and afile access client.

The storage device cluster 28 may be storage device such as a lowperformance integrated drive electronics (IDE for short) disk or aserial advanced technology attachment (SATA for short) disk, a highperformance solid state disk (SSD for short), a serial attached SCSI(SAS for short, wherein the SCSI is short for a small computer systeminterface), and an SATA.

FIG. 3 is a flowchart of a storage method for a distributed file systemaccording to an example embodiment of the disclosure. As shown in FIG.3, the following steps are included:

Step S302, a file access client (FAC for short) initiates a readingrequest for a file 1 to a file location register (FLR for short).

Step S304, the FLR checks whether a tiered storage switch is turned on.If so, step S308 is executed; otherwise, step S306 is executed.

Step S306, a fragment migration flow of tiered storage is ended.

Step S308, a file access server reports the IOPS of each disk each timewhen a timer expires, and the tiered storage state of a disk exceeding atiered storage threshold value is set as open.

Step S310, the enthusiasm degree of the file is calculated according toreading request times and frequency.

Step S312, whether it is a hot file is judged. If so, step S316 isexecuted; otherwise, step S314 is executed.

Step S314, the fragment is not migrated, and the fragment of the nextreading request is checked.

Step S316, it is checked, based on a timer, whether the IOPS of eachdisk has recovered to a value less than a warning value. If so, stepS318 is executed; otherwise, step S320 is executed.

Step S318, the migration of the fragment of the hot file in the disk isstopped.

Step S320, the fragment is extracted to be migrated.

It should be noted that, compared to the normal fragment migration flowused for disk space balancing, the tiered storage initiated due to ahigh access enthusiasm operates at a higher priority so as to ensure thefluency for a user to access a file.

In another example embodiment, the steps are as follows:

Step 1, observing an IOPS load of a disk on a network managementinterface and recording an initial value;

step 2, turning on a tiered storage switch on the network managementinterface and parameters coming into effect immediately;

step 3, configuring a disk IOPS threshold value on the networkmanagement interface and parameters coming into effect immediately;

step 4, checking whether hot file migration has started and when themigration will end in a log; and

step 5, after the migration ends, observing the IOPS load of the disk onthe network management interface, comparing the previous load exceedinga critical value with a load after migration, if the IOPS load after themigration decreases to a value less than the critical value, which showsthat the setting of the threshold value is relatively reasonable, and ifthe TOPS load after the migration is still above the critical value,repeating step 3 and decreasing the IOPS threshold value.

It should be noted that the steps shown in the flowchart of the drawingscan be executed, for example, in a computer system with a set ofinstructions executable by a computer, in addition, a logic order isshown in the flowchart, but the shown or described steps can be executedin a different order under some conditions.

The embodiments of the disclosure also provide a storage apparatus for adistributed file system, applied to a metadata server, and the storageapparatus for a distributed file system may be used for achieving theabove-mentioned storage method for a distributed file system. FIG. 4 isa structural block diagram of a storage apparatus for a distributed filesystem according to an embodiment of the disclosure. As shown in FIG. 4,the apparatus includes a first determination component 42 and amigration component 44. The structure will be described below indetails.

The first determination component 42 is configured to determine accesstimes to a same file in preset time; and the migration component 44 iscoupled to the first determination component 42 and is configured tomigrate the file to a storage device with higher performance than thatof a current storage device according to the access times determined bythe first determination component 42.

In the relevant art, the problem of the load brought to the disk byhigh-frequency access to a hot file when reading out a file is notsolved. In the embodiments of the disclosure, tiered storage isperformed on files in the distributed file system according to accessenthusiasm of the files, that is, a file with a high access frequency inthe preset time is migrated to a storage device with high performance,and a file fragment storage location is associated with file fragmentaccess enthusiasm through differential storage, so that IOPS pressurebetween storage devices is balanced and the overall performance isimproved.

As shown in FIG. 5, the migration component 44 includes: a firstdetermination unit 442, configured to determine that the access timesexceed a preset threshold value; a second determination unit 444,coupled to the first determination unit 442, and configured todetermine, from all storage devices, a storage device with higherperformance than that of the current storage device and having an idleblock; and a migration unit 446, coupled to the second determinationunit 444, and configured to migrate the file to the storage devicedetermined by the second determination unit 444.

In an example embodiment, the migration component 44 further includes: asetting unit, coupled to the first determination unit 442, andconfigured to set an access enthusiasm attribute of the file as hot.

As shown in FIG. 6, the above-mentioned apparatus further includes: asecond determination component 46, configured to respectively determinean TOPS limit and a current IOPS of each storage device; a calculationcomponent 47, coupled to the second determination component 46, andconfigured to respectively calculate a ratio of the current IOPS to theIOPS limit of each storage device; a comparison component 48, coupled tothe calculation component 47, and configured to respectively compare theratio with a preset critical value; and a third determination component49, coupled to the comparison component 48, and configured to, if theratio is greater than the preset critical value, determine that it isneeded to migrate the file with higher access times than a presetthreshold value in a current storage device.

In an example embodiment, the above-mentioned apparatus furtherincludes: a receiving component, coupled to the third determinationcomponent 49, and configured to receive a reading request for the file,and add one to the access times to the file.

In an example embodiment, the above-mentioned apparatus furtherincludes: a checking component, configured to check whether a ratio of acurrent IOPS to an IOPS limit of each storage device is not greater thana critical value according to a predetermined period; a first processingcomponent, coupled to the checking component, and configured to, if theratio value is not greater than the critical value, stop migrating thefile in a current storage device; and a second processing component,coupled to the checking component, and configured to, if the ratio isgreater than the critical value, continue migrating the file with higheraccess times than a preset threshold value in the current storagedevice.

It should be noted that the storage apparatus for a distributed filesystem described in the apparatus embodiments corresponds to theabove-mentioned method embodiments, with the specific implementationbeing described in the method embodiment in detail, thereby needing nofurther description.

It should be noted that the above-mentioned solution may be applied to adistributed file system having a metadata server, but may not be appliedto a general storage system.

In conclusion, according to the embodiments above of the disclosure, astorage method and apparatus for a distributed file system are provided.In the disclosure, tiered storage is performed on files in thedistributed file system according to access enthusiasm of the files,that is, a file with a high access frequency in the preset time ismigrated to a storage device with high performance, and a file fragmentstorage location is associated with file fragment access enthusiasmthrough differential storage, so that IOPS pressure between storagedevices is balanced and the overall performance is improved. The maximumusage of the compatibility and performance of storage devices withdifferent performances are achieved. By means of migrating a file with ahigh enthusiasm degree to a storage device with higher performance, theshort slab problem of the storage method in a hybrid storage deviceenvironment in the related art is significantly released, and loadbalancing between different storage devices is achieved, therebyimproving the overall performance of storage devices in a heterogeneousstorage mode.

Obviously, those skilled in the art shall understand that theabove-mentioned components and steps of the disclosure can be realizedby using general purpose calculating device, can be integrated in onecalculating device or distributed on a network which consists of aplurality of calculating devices. Alternatively, the components and thesteps of the disclosure can be realized by using the executable programcode of the calculating device. Consequently, they can be stored in thestoring device and executed by the calculating device, or they are madeinto integrated circuit component respectively, or a plurality ofcomponents or steps thereof are made into one integrated circuitcomponent. In this way, the disclosure is not restricted to anyparticular hardware and software combination.

The above description is only example embodiments of the disclosure andis not intended to limit the disclosure, and the disclosure can have avariety of changes and modifications for those skilled in the art. Anymodification, equivalent replacement, or improvement made within theprinciple of the disclosure shall all fall within the protection scopeas defined by the appended claims of the disclosure.

1. A storage method for a distributed file system, comprising:determining access times to a same file in preset time; and migratingthe file to a storage device with higher performance than that of acurrent storage device according to the access times.
 2. The methodaccording to claim 1, wherein migrating the file to the storage devicewith higher performance than that of the current storage deviceaccording to the access times comprises: determining that the accesstimes exceed a preset threshold value; determining, from all storagedevices, a storage device with higher performance than that of thecurrent storage device and having an idle block; and migrating the fileto the determined storage device.
 3. The method according to claim 2,wherein after determining that the access times exceed the presetthreshold value, the method further comprises: setting an accessenthusiasm attribute of the file as hot.
 4. The method according toclaim 1, wherein before determining the access times to a same file inpreset time, the method further comprises: respectively determining aninput/output operation per second (IOPS) limit and a current IOPS ofeach storage device in the distributed file system; respectivelycalculating a ratio of the current IOPS to the IOPS limit of eachstorage device; and respectively comparing the ratio with a presetcritical value; and if the ratio is greater than the preset criticalvalue, determining that it is needed to migrate the file with higheraccess times than a preset threshold value in a current storage device.5. The method according to claim 4, wherein after determining that it isneeded to migrate the file with higher access times than the presetthreshold value in the current storage device, the method furthercomprises: receiving a reading request for the file, and adding one tothe access times to the file.
 6. The method according to claim 1,wherein before determining the access times to a same file in presettime, the method further comprises: a file access server calculating anIOPS of a storage device corresponding to the file access server; andthe file access server reporting the IOPS to a metadata server accordingto a predetermined period.
 7. The method according to claim 1, whereinafter migrating the file to the storage device with higher performancethan that of the current storage device according to the access times,the method further comprises: checking whether a ratio of a current IOPSto an IOPS limit of each storage device is not greater than a criticalvalue according to a predetermined period; if the ratio value is notgreater than the critical value, stopping migrating the file in thecurrent storage device; and if the ratio is greater than the criticalvalue, continuing migrating the file with higher access times than apreset threshold value in the current storage device.
 8. A storageapparatus for a distributed file system, wherein the storage apparatusis applied to a metadata server and comprises: a first determinationcomponent, configured to determine access times to a same file in presettime; and a migration component, configured to migrate the file to astorage device with higher performance than that of a current storagedevice according to the access times.
 9. The apparatus according toclaim 8, wherein the migration component comprises: a firstdetermination unit, configured to determine that the access times exceeda preset threshold value; a second determination unit, configured todetermine, from all storage devices, a storage device with higherperformance than that of the current storage device and having an idleblock; and a migration unit, configured to migrate the file to thedetermined storage device.
 10. The apparatus according to claim 8,wherein the apparatus further comprises: a second determinationcomponent, configured to respectively determine an input/outputoperation per second (IOPS) limit and a current IOPS of each storagedevice; a calculation component, configured to respectively calculate aratio of the current IOPS to the IOPS limit of each storage device; acomparison component, configured to respectively compare the ratio witha preset critical value; and a third determination component, configuredto, if the ratio is greater than the preset critical value, determinethat it is needed to migrate the file with higher access times than apreset threshold value in a current storage device.
 11. The methodaccording to claim 2, wherein after migrating the file to the storagedevice with higher performance than that of the current storage deviceaccording to the access times, the method further comprises: checkingwhether a ratio of a current IOPS to an IOPS limit of each storagedevice is not greater than a critical value according to a predeterminedperiod; if the ratio value is not greater than the critical value,stopping migrating the file in the current storage device; and if theratio is greater than the critical value, continuing migrating the filewith higher access times than a preset threshold value in the currentstorage device.
 12. The method according to claim 3, wherein aftermigrating the file to the storage device with higher performance thanthat of the current storage device according to the access times, themethod further comprises: checking whether a ratio of a current IOPS toan IOPS limit of each storage device is not greater than a criticalvalue according to a predetermined period; if the ratio value is notgreater than the critical value, stopping migrating the file in thecurrent storage device; and if the ratio is greater than the criticalvalue, continuing migrating the file with higher access times than apreset threshold value in the current storage device.
 13. The methodaccording to claim 4, wherein after migrating the file to the storagedevice with higher performance than that of the current storage deviceaccording to the access times, the method further comprises: checkingwhether a ratio of a current IOPS to an IOPS limit of each storagedevice is not greater than a critical value according to a predeterminedperiod; if the ratio value is not greater than the critical value,stopping migrating the file in the current storage device; and if theratio is greater than the critical value, continuing migrating the filewith higher access times than a preset threshold value in the currentstorage device.
 14. The method according to claim 5, wherein aftermigrating the file to the storage device with higher performance thanthat of the current storage device according to the access times, themethod further comprises: checking whether a ratio of a current IOPS toan IOPS limit of each storage device is not greater than a criticalvalue according to a predetermined period; if the ratio value is notgreater than the critical value, stopping migrating the file in thecurrent storage device; and if the ratio is greater than the criticalvalue, continuing migrating the file with higher access times than apreset threshold value in the current storage device.
 15. The methodaccording to claim 6, wherein after migrating the file to the storagedevice with higher performance than that of the current storage deviceaccording to the access times, the method further comprises: checkingwhether a ratio of a current IOPS to an IOPS limit of each storagedevice is not greater than a critical value according to a predeterminedperiod; if the ratio value is not greater than the critical value,stopping migrating the file in the current storage device; and if theratio is greater than the critical value, continuing migrating the filewith higher access times than a preset threshold value in the currentstorage device.
 16. The apparatus according to claim 9, wherein themigration component further comprises: a setting unit, configured to setan access enthusiasm attribute of the file as hot.
 17. The apparatusaccording to claim 10, wherein the apparatus further comprises: areceiving component, configured to receive a reading request for thefile, and add one to the access times to the file.
 18. The apparatusaccording to claim 8, wherein the apparatus further comprises: achecking component, configured to check whether a ratio of a currentIOPS to an IOPS limit of each storage device is not greater than acritical value according to a predetermined period; a first processingcomponent, configured to, if the ratio value is not greater than thecritical value, stop migrating the file in a current storage device; anda second processing component, coupled to the checking component, andconfigured to, if the ratio is greater than the critical value, continuemigrating the file with higher access times than a preset thresholdvalue in the current storage device.
 19. The apparatus according toclaim 9, wherein the apparatus further comprises: a checking component,configured to check whether a ratio of a current IOPS to an IOPS limitof each storage device is not greater than a critical value according toa predetermined period; a first processing component, configured to, ifthe ratio value is not greater than the critical value, stop migratingthe file in a current storage device; and a second processing component,coupled to the checking component, and configured to, if the ratio isgreater than the critical value, continue migrating the file with higheraccess times than a preset threshold value in the current storagedevice.
 20. The apparatus according to claim 10, wherein the apparatusfurther comprises: a checking component, configured to check whether aratio of a current IOPS to an IOPS limit of each storage device is notgreater than a critical value according to a predetermined period; afirst processing component, configured to, if the ratio value is notgreater than the critical value, stop migrating the file in a currentstorage device; and a second processing component, coupled to thechecking component, and configured to, if the ratio is greater than thecritical value, continue migrating the file with higher access timesthan a preset threshold value in the current storage device.